Interested in Language
"If the Taniyama-Shimura conjecture was true it would enable mathematicians to tackle elliptic problems that had remained unsolved for centuries by approaching them through the modular world." (From Fermat's Enigma by Simon Singh)
In the above quotation the indicative form "was" was used instead of the subjunctive one "were." I think we have three possibilities here:
When the text was written ...
1) The conjecture was already known to be true, so the indicative "was" is used. (This is the actual case, when that book was written that conjecture had indeed been proved to be true.)
2) The conjecture is now known to be false. The subjunctive case "were" should be used. (This is not the actual case.)
3) The conjecture is still open, nobody knows whether it is true or not. In this case one should use "was" or "were"? (This is not the actual case.)
I would like to ask you whether you agree or not with my interpretations in (1) and (2) and I need help to answer the case (3).
2) The conjecture is now known to be false. The subjunctive case "were" should be used. (This is not the actual case.
I disagree with this part, if the conjecture is now known to be false, "had been" should be used: "If the Taniyama-Shimura conjecture had been true..."